High-pressure study of oxo-bridged mixed-valent mniii/mn iv dimers

Abstract

A combination of high-pressure single crystal X-ray diffraction and high-pressure SQUID magnetometry has been used to study two oxo-bridged mixed-valent MnIII/MnIV dimers. [Mn2O 2(bpy)4](ClO4)3 3CH3CN, (1.3CH3CN; bpy=2,2́-bipyridine) has been compressed to 2.0 GPa whilst [Mn 2O2(bpy)4](PF6)3 2CH 3CN 1H2O, (2.2CH3CN 1H2O) could be measured crystallographically up to 4.55 GPa. The PF6 salt of [Mn2O2 (bpy) 4]3+ has never been reported before while 1 has been reported as a hydrate and in a different crystallographic space group. The application of hydrostatic pressure imposes significant distortions and modifications in the structures of both complexes. In particular, in complex 1.3CH3CN the Mn-Mn separation is reduced by the contraction of some of the Mn-O bond lengths, whilst in 2.2CH3CN 1H2O the Mn-O-Mn bridging angles and the Mn-O bond lengths are substantially unchanged. Interestingly 2.2CH3CN 1H2O also shows a constant contraction in nearly all the Mn-N bonds. The magnetic behaviour of the complexes has been measured up to 0.87 GPa for 1.3CH 3CN and 0.84 GPa for 2.2CH3CN 1H2O. © 2010 Verlag der Zeitschrift für Naturforschung, Tübingen.